1. Field of the Invention
The present invention relates to a laminate structure from which a metal wire embedded substrate is produced. More specifically, the present invention relates to a laminate structure in which a metal wire embedded substrate layer as a flexible substrate is easily separated from a carrier substrate, enabling the fabrication of a device (for example, a flexible display device) having the flexible substrate in an easier manner.
2. Description of the Related Art
Flexible electronics, for example, flexible displays, solar cells, area lighting devices, e-papers, flexible secondary batteries, and touch panels, have recently received attention as promising technologies.
Flexible electronics have developed to make inexpensive, easy-to-bend, and transparent electronic devices and systems. Techniques for producing flexible substrates including transparent electrodes with low resistance are essentially needed to realize flexible electronics.
Several approaches are known to reduce the resistance of metal wires, for example, (1) by reducing the resistivity (ρ) of the wires, (2) by decreasing the length of the wires, or (3) by increasing the height (thickness) of the wires.
For approach (1), however, resistivity limits the choice of materials. Copper is presently the most widely used material due to its sufficiently low resistivity. Other materials, such as silver, are only available at high prices, limiting their use. Approach (2) is physically limited by the problems associated with the circuit design described in Korean Patent Publication No. 10-2014-0008606. In view of the limitations of approaches (1) and (2), approach (3) is considered acceptable. However, as the height of wires increases, many problems arise, for example, disordered alignment of the wires, electrical shorting, short circuiting between the wires, and damage to the wires.
Thus, there is a need to insert metal wires into a substrate. In this connection, conventional techniques include etching techniques for forming a desired pattern of metal wires by deposition and etching and damascene techniques for damascening wires into grooves formed in an insulating film by applying CMP to a film, such as a copper (Cu) thin film, which is difficult to dry etch for patterning.
However, such conventional techniques require consumption of large amounts of materials by repeated deposition/etching, involve complicated processing steps, and cause thermal damage to a plastic substrate upon thermal treatment of a metal layer formed in the plastic substrate.
To solve the above problems, a proposal has been made on a technique wherein metal wires are formed on a hard substrate, a curable polymer is coated and cured thereon, and the hard substrate is mechanically peeled. However, according to this technique, when the hard substrate is forcibly peeled from the metal wire embedded polymer substrate, damage to the metal wires and the polymer substrate is caused, leading to defects in a final product. Portions of the hard substrate remain unremoved from the polymer substrate and act as impurities.
Under such circumstances, a method has been proposed in which a water or organic solvent soluble or photodegradable sacrificial layer is formed on a carrier substrate, a metal wire embedded flexible substrate layer is formed on the sacrificial layer, and the sacrificial layer is removed to separate and recover the flexible substrate from the carrier substrate (Korean Patent Publication No. 10-2014-0028243). According to this method, however, removal of the sacrificial layer by dissolution in water or an organic solvent or photodecomposition increases the costs associated with the treatment of the water or organic solvent after use.